SPI Ultrasound Physics Review Exam - Questions and Answers

SPI Ultrasound Physics Review Exam - Questions and Answers Relates to likelihood of harmful bio effects from cavitation Mechanical index Predicts maximum temperature increase Thermal index Measures output intensity of the beam Hydrophone Region of increased brightness due to higher intensities in focal zone Focal banding Occurs when sound travels through a medium with a lower attenuation rate than the surrounding tissue Enhancement Beam travels through an area of high attenuation Shadowing Beam may travel through adjacent solid and cystic areas causing the cyst to appear to have internal echoes Slice or section thickness If the actual propagation speed is > 1540 m/s it was be displayed _________ to the transducer Too close If actual propagation speed is < 1540 m/s it will be displayed ________ to the transducer Too far away Acoustic energy emitted in a different direction than the primary beam, reflectors can appear in the wrong place Side/grating lobes Slicing an element into smaller sub elements, reduces grating lobes Subdicing Beam hits a curved speculate reflector and is sent off in another direction Edge shadowing Edge shadowing is caused by _______ and is reduced by _______ Refraction, spatial compounding ______ errors cause reflectors to appear at a different location on the display than the actual anatomical location Refraction Sound beam bounces off a strong reflector and reflects the sound toward another reflector chasing a duplicate object Mirror image artifact Closely spaced parallel echoes Comet tail What type of artifact is comet tail? Reverberation Artifact caused by vibration of air or very small metal objects, indicates air Ring down Error in the image that does not represent a atomic information Artifact Doppler analysis: fast but not as accurate, color Doppler Autocorrelation Doppler analysis: slow but accurate, spectral Doppler (CW, PW) Fast Fourier transform What is aliasing? When the Doppler shift is greater than the nyquist limit What is the nyquist limit? 1/2 PRF What is a color bruit? When a stenosis, AV fistula or pseudoaneurysm causes a tissue vibration Motion artifact seen with power Doppler Flash artifact Mirror artifact occurs when Doppler gain is too high or angle is too close to 90 degrees How can you eliminate clutter? Wall filter